Effect of carotid corrected flow time combined with perioperative fluid therapy on preventing hypotension after general anesthesia induction in elderly patients: a prospective cohort study

Background: Hypotension often occurs following the induction of general anesthesia in elderly patients undergoing surgery and can lead to severe complications. This study assessed the effect of carotid corrected flow time (FTc) combined with perioperative fluid therapy on preventing hypotension after general anesthesia induction in elderly patients. Materials and methods: The prospective cohort study was divided into two parts. The first part (Part I) consisted of 112 elderly patients. Carotid FTc was measured using Color Doppler Ultrasound 5 min before anesthesia induction. Hypotension was defined as a decrease of greater than 30% in systolic blood pressure (SBP) or a decrease of greater than 20% in mean arterial pressure (MAP) from baseline, or an absolute SBP below 90 mmHg and MAP below 60 mmHg within 3 min after induction of general anesthesia. The predictive value of carotid FTc was determined using receiver operating characteristic (ROC) curve. The second part (Part II) consisted of 65 elderly patients. Based on the results in Part I, elderly patients with carotid FTc below the optimal cut-off value received perioperative fluid therapy at a volume of 8 ml/kg of balanced crystalloids (lactated Ringer's solution) in 30 min before induction. The effect of carotid FTc combined with perioperative fluid therapy was assessed by comparing observed incidence of hypotension after induction. Results: The area under the ROC for carotid FTc to predict hypotension after induction was 0.876 [95% confidence interval (CI) 0.800-0.952, P<0.001]. The optimal cut-off value was 334.95 ms (sensitivity of 87.20%; specificity of 82.20%). The logistic regression analysis revealed that carotid FTc is an independent predictor for post-induction hypotension in elderly patients. The incidence of post-induction hypotension was significantly lower (P<0.001) in patients with carotid FTc less than 334.95 ms who received perioperative fluid therapy (35.71%) compared to those who did not (92.31%). Conclusions: Carotid FTc combined with the perioperative fluid therapy could significantly reduce the incidence of hypotension after the induction of general anesthesia in elderly patients.